In a liquid crystal display device, a liquid crystal is a substance that does not itself illuminate light. Instead, the liquid crystal relies on light received from a light source, thereby displaying images and data. In the case of a typical liquid crystal display, a backlight module powered by electricity supplies the needed light.
Generally, backlight modules can be classified into an edge lighting type or a bottom lighting type based upon the location of lamps within the devices. The edge lighting type backlight module has a lamp unit arranged at a side portion of a light guiding plate for guiding light. The edge lighting type backlight modules are commonly employed in small-sized LCD due to their lightweight, small size, and low electricity consumption. A bottom lighting type backlight module has a plurality of lamps arranged at regular positions to directly illuminate an entire surface of an LCD panel. The bottom lighting type backlight modules have a higher efficiency of light usage and a longer operational lifetime than the edge lighting type backlight modules, the bottom lighting type backlight modules are especially used in large-sized LCD devices.
Referring to FIG. 8, a typical direct type backlight module 1 is shown. The backlight module 1 includes a plurality of lamp tubes 10 and a lamp housing 11. Each lamp tube 10 includes two electrodes (not shown) defined at two ends thereof and two electrode holders 102 receiving the two electrodes respectively. The lamp housing 11 includes a base 110, a plurality of side protrusions 112 protruding out from two corresponding opposite edges of the base 110, the side protrusions 112 being disposed apart side by side, and a plurality of cutouts 114 each defined in the base 110 between two adjacent side protrusions 112. The cutouts 114 are used to receive the electrode holders 102 defined by the lamp tubes 10, thus each lamp tube 10 is positioned between the two corresponding adjacent side protrusions 112.
However, the side protrusions 112 are formed of thin metal sheet. This results in that the side protrusions 112 can easily be distorted or twisted by an exterior force or sudden impact. Therefore, a mechanical intensity of the lamp housing 11 can be insufficient. In addition, although the structures of the lamp housing 11 helps to position the lamp tubes 10 in a parallel formation, the lamp tubes 10 are not fixed to the lamp housing 11 tightly. This results in that the lamp tubes 10 can easily be damaged by a sudden impact.
What is needed, therefore, is a direct type backlight module that overcome the above mentioned disadvantage.